1. Cross Reference to Related Applications
The subject matter of the present application is related to co-pending application "LATCHING PRODUCTION SEAL ASSEMBLY", by Sidney Kenneth Smith, Jr., U.S. Ser. No. 809,356 filed 12/16/85 now U.S. Pat. No. 4,655,290, and assigned to the assignee of the present invention.
2. Field of the Invention
The present invention relates to seal assemblies of the type used to seal within a liner in a well, to connect a tubing string within the liner for the production of well bore fluids and, specifically, to such a seal assembly which includes an integral landing unit for receiving a plug to temporarily close off the well during remedial work.
3. Description of the Prior Art
Oil and gas wells are completed by installing a production casing or "liner" into the hole from the surface and cementing the liner in place. The liner is typically provided with a setting sleeve having an internally threaded region which is engaged by the external threads of a conventional running tool. The running tool is used to lower the liner to the proper depth within the well, and to apply setting force to "hang" the liner from gripping members within the well bore.
After the liner has been hung and cemented in place, the liner is perforated at the producing depth and the oil and/or gas flows from the surrounding earthern formation through the perforations and up the liner to the surface, usually through production tubing.
In the past, a section of the liner interior, or a connection thereto, was typically provided with a highly machined "polished bore" for receiving the lower extent of the production tubing string. The tubing string was provided with external seals which formed a sliding seal within the polished bore, thereby allowing the tubing string to have a "stroke" to compensate for temperature and pressure variations in the well.
It was also desirable to provide a retrievable landing unit or "landing nipple", with an internal profile, below the seal region so that a plug could be seated in the profile to temporarily close off production without killing the well. In this way, the production string could be pulled to the well surface and remedial work could be performed on the well. Once the work was complete, the production string could be reinstalled and the plug removed. The landing nipple itself could be retrieved to the well surface to provide a full bore through the liner, if desired.
The use of a landing nipple below the sliding seal generally required a two trip installation procedure. One trip into the well was required to install the landing nipple. Another trip was then required to install the production tubing string.
The present invention has as its object the provision of a combination retrievable landing unit and production seal assembly which is run and installed in the liner in a one trip operation.
Another object of the invention is the provision of a landing unit and seal assembly which can be latched into the internally threaded surface of the liner setting sleeve. These are the same threads which are engaged by the liner running tool during the installation of the liner within the well bore and prior to retrieving the running tool to the well surface.
Another object of the invention is the provision of a landing unit and seal assembly with a backup release mechanism which allows a straight pull release as a safety measure in addition to a standard release effected by right hand rotation of the tubing string from the well surface.